This invention relates to methods for creating transgenic plants through the use of transposons. More specifically, it relates to a system that provides transformed plants that contain a minimum amount of ancillary foreign genetic material. In addition, methods are provided for molecular fingerprinting proprietary cultivars using transposons and other introduced DNA sequences.
The production of transgenic plants opens an exciting field with the promise that innumerable desirable characteristics may be incorporated into the plants society depends upon. For example, due to the environmental concerns and other costs incurred with the use of chemical pesticides, the ability to develop plants which are naturally resistant to pests is paramount.
Using current transformation procedures, however, only about one out of every one million plant cells is transformed. The problem of transformation then translates into identifying the single cell that has been transformed in this background of untransformed cells. This problem has been addressed generally by physically linking a gene, typically a bacterial gene that confers antibiotic resistance, to the desired gene. The cell that has taken up the desired gene can then be selected by its ability to grow on a medium containing the particular antibiotic. Untransformed plant cells do not contain the resistance gene and, thus, do not grow.
The presence of antibiotic resistance genes and other ancillary sequences in the final cultivar is particularly undesirable, however. These ancillary sequences are necessary for the transformation processes, but they do not positively contribute to the final cultivar and in fact lessen its desirability to the consumer. In the public perception, transfer of sequences between widely separated taxonomic groups is of greater concern than transfer between more closely related groups. Thus, a transgenic cultivar bearing sequences from a bacterium may be more objectionable than one bearing sequences from a wild species in the same genus. To increase public acceptance of transgenic plants, it is extremely important to eliminate bacterial resistance genes and other ancillary sequences from the cultivar. The biological effects of the insertion of this unwanted genetic material is unclear. Transgenic plants have thus been met with resistance and skepticism in large part because of the uncertainty associated with the ancillary genetic material.
The presence of these undesirable sequences may also complicate the regulatory procedures necessary to bring the cultivar to the market place. The current regulatory structure bases the degree of scrutiny required for release of transgenic organisms in part on the taxonomic difference between the host organism and the source of the inserted sequence.
A reliable method for eliminating the unwanted ancillary sequences would thus improve commercial viability by increasing public acceptance and simplifying the regulatory process. The prior art has not recognized the importance of this problem, nor has it worked to provide a solution.
Currently, the cost of developing improved crop varieties is extremely high. Thus, it is imperative that commercial cultivars be protected from use by competitive breeders. Current methods of varietal protection require a detailed description of the physical appearance and biochemical attributes of the cultivar which make it unique. However, this type of characterization is subjective and difficult to practice because physiological attributes can easily vary under different growth conditions. Additionally, the use of a protected variety as a parent in a hybrid combination is virtually impossible to detect by description methods because the parental characteristics will be masked in the hybrid. Thus, a reliable method for definitively identifying a proprietary cultivar is required, but lacking in the art.